Lower bound of the (possibly infinite) radius of the universe, if it is a 3-sphere, according to one estimate using the WMAP data at 95% confidence.[41] It equivalently implies that there are at minimum 21 particle horizon-sized volumes in the universe.

1.6 × 10−11yoctometres (1.6 × 10−35 metres) – the Planck length (Measures of distance shorter than this are considered nonsensical and do not make any physical sense, according to current theories of physics).

1 ym – 1 yoctometre, the smallest named subdivision of the metre in the SIbase unit of length, one septillionth of a metre.

Comparison of sizes of semiconductor manufacturing process nodes with some microscopic objects and visible light wavelengths. At this scale, the width of a human hair is about 10 times that of the image.[50]

15 metres – approximate distance the tropical circles of latitude are moving towards the equator and the polar circles are moving towards the poles each year due to a natural, gradual decrease in the Earth's axial tilt

A length of 100 kilometres (about 62 miles), as a rough amount, is relatively common in measurements on Earth and for some astronomical objects, it is the altitude at which the FAI defines spaceflight to begin. To help compare orders of magnitude, this section lists lengths between 100 and 1,000 kilometres (105 and 106metres).

Small planets, the Moon and dwarf planets in our solar system have diameters from one to ten million metres. Top row: Mars (left), Mercury (right); bottom row: Moon (left), Pluto (center), and Haumea (right), to scale.

Planets from Venus up to Uranus have diameters from ten to one hundred million metres. Top row: Uranus (left), Neptune (right); middle row: Earth (left), Sirius B (center), and Venus (right), to scale.

Rigel and Aldebaran (top left and right) compared to smaller stars, the Sun (very small dot in lower middle, with orbit of Mercury as yellow ellipse) and transparent sphere with radius of one light minute.

Comparison of size of the Kuiper belt (large faint torus) with the star VY Canis Majoris (at its previous estimate, within Saturn's orbit), Betelgeuse (inside Jupiter's orbit) and R Doradus (small central red sphere) together with the orbits of Neptune and Uranus, to scale. The yellow ellipses represent the orbits of each planet and the dwarf planet Pluto.

Sedna's orbit (left) is longer than 100 Tm, but other lengths are between 10 and 100 Tm: Comet Hale-Bopp's orbit (lower, faint orange); one light-day (yellow spherical shell with yellow Vernal point arrow as radius); the heliosphere's termination shock (blue shell); and other arrows show positions of Voyager 1 (red) and Pioneer 10 (green). Click on image for larger view and links to other scales.

Lengths with order of magnitude 1e18m: thousand light year radius circle with yellow arrow and 100 light year circle at right with globular cluster Messier 5 within and Carina Nebula in front; globular cluster Omega Centauri to left of both; part of the 1400 light year wide Tarantula Nebula fills the background.

This list includes distances between 1 and 10 exametres (1018 m). To help compare different distances this section lists lengths between 1018m (1 Em or 105.7 light years) and 1019 m (1057 light years).

^ ab10115 is 1 followed by 115 zeroes, or a googol multiplied by a quadrillion. 1010115 is 1 followed by a quadrillion googol zeroes. 101010122is 1 followed by 1010122 (a googolplex10 sextillion) zeroes.

^gravitational waves that originate tens of millions of light years from Earth are expected to distort the 4 kilometre mirror spacing by about 10−18 m, less than one-thousandth the charge diameter of a proton. Equivalently, this is a relative change in distance of approximately one part in 1021. "On 14 September 2015 at 09:50:45 UTC the two detectors of the Laser Interferometer Gravitational-Wave Observatory simultaneously observed a transient gravitational-wave signal. The signal sweeps upwards in frequency from 35 to 250 Hz with a peak gravitational-wave strain of 1.0×10−21." B. P. Abbott et al. (LIGO Scientific Collaboration and Virgo Collaboration), "Observation of Gravitational Waves from a Binary Black Hole Merger", Phys. Rev. Lett. 116, 061102, published 11 February 2016.

^ abRoberts, Richard W. (1975-06-01). Metric System of Weights and Measures - Guidelines for Use. USA: Director of the National Bureau of Standards. Federal Register FR Doc.75-15798 (1975-06-18). Accordingly, the following units and terms listed in the table of metric units in section 2 of the act of 28 July 1866, that legalized the metric system of weights and measures in the United States, are no longer accepted for use in the United States: myriameter, stere, millier or tonneau, quintal, myriagram, kilo (for kilogram).

1.
Level3 (Perfume album)
–
Level3 is the fourth studio album by Japanese girl group Perfume. It was released on October 2,2013 by Universal J, recorded in Japanese and English language, Level3 is an electronic dance album that borrows numerous musical elements including J-pop, house music, and technopop. Level3 was recorded and mixed in Japan, with the assistance of Nakata, six different formats were released to promote the album, a standalone CD, a limited CD and DVD bundle, and a digital release. It was re-released in May 2014 as an additional bonus CD standalone edition, a 12-inch double LP, upon the albums release, it was met with favourable reviews from music critics. Critics noted the improvement from their previous release, and commended Nakatas production standards. Level3 was listed by critics as one of the best albums of 2013. It became Perfumes fourth studio album to reach the top spot on Japans Oricon Albums Chart, the album charted on Koreas Gaon Album Chart and Taiwans G-Music Albums Chart. Four singles were released from Level3, including one promotional and its lead single Spring of Life reached number two on Japans Oricon Singles Chart and atop the Japan Hot 100 chart. The second, third, and fourth singles, Spending All My Time, Mirai no Museum, each single was certified gold by the RIAJ company, Perfumes only album to achieve this. Promotional single 1mm reached number nine on the Japan Hot 100 chart, Perfume promoted the album on their 2013 Dome Tour. In February 2012, Perfume departed from Tokuma Japan Communications and signed a deal with Universal Music Japan in order to release their work through global markets, two months later, Perfume announced their established self-titled vanity label that would co-release all of their material with Universal Music Japan. They later confirmed the label was to published their overseas releases, in August 2013, Perfume announced the release of their fourth studio album entitled Level3. Perfume began recording the album in Japan around mid-2012 with Nakata, the material from Level3 took nearly two years to produce and record, making it one of Perfumes longer spanning projects to date. This is due to Perfumes scheduling conflicts with studio time and live performances at concerts, the material marks Perfumes fourth consecutive studio album to be fully composed, written, and arranged by Nakata. We prefer not to practice too much in advance, if we listen too much, or practice too much, before the recording, our habits tend to overcome the freshness. Perfume member A-Chan viewed Level3 as an album, stating We see each album as being like a concept album. So Perfume right now is at a music stage. This doesn’t mean we’re going in this direction from here but this is just one of our aspects, Level3 is an electronic dance album that borrows numerous musical elements including pop, house music, and technopop

2.
Length
–
In geometric measurements, length is the most extended dimension of an object. In the International System of Quantities, length is any quantity with dimension distance, in other contexts length is the measured dimension of an object. For example, it is possible to cut a length of a wire which is shorter than wire thickness. Length may be distinguished from height, which is vertical extent, and width or breadth, length is a measure of one dimension, whereas area is a measure of two dimensions and volume is a measure of three dimensions. In most systems of measurement, the unit of length is a base unit, measurement has been important ever since humans settled from nomadic lifestyles and started using building materials, occupying land and trading with neighbours. As society has become more technologically oriented, much higher accuracies of measurement are required in a diverse set of fields. One of the oldest units of measurement used in the ancient world was the cubit which was the length of the arm from the tip of the finger to the elbow. This could then be subdivided into shorter units like the foot, hand or finger, the cubit could vary considerably due to the different sizes of people. After Albert Einsteins special relativity, length can no longer be thought of being constant in all reference frames. Thus a ruler that is one meter long in one frame of reference will not be one meter long in a frame that is travelling at a velocity relative to the first frame. This means length of an object is variable depending on the observer, in the physical sciences and engineering, when one speaks of units of length, the word length is synonymous with distance. There are several units that are used to measure length, in the International System of Units, the basic unit of length is the metre and is now defined in terms of the speed of light. The centimetre and the kilometre, derived from the metre, are commonly used units. In U. S. customary units, English or Imperial system of units, commonly used units of length are the inch, the foot, the yard, and the mile. Units used to denote distances in the vastness of space, as in astronomy, are longer than those typically used on Earth and include the astronomical unit, the light-year. Dimension Distance Orders of magnitude Reciprocal length Smoot Unit of length

3.
Metre
–
The metre or meter, is the base unit of length in the International System of Units. The metre is defined as the length of the path travelled by light in a vacuum in 1/299792458 seconds, the metre was originally defined in 1793 as one ten-millionth of the distance from the equator to the North Pole. In 1799, it was redefined in terms of a metre bar. In 1960, the metre was redefined in terms of a number of wavelengths of a certain emission line of krypton-86. In 1983, the current definition was adopted, the imperial inch is defined as 0.0254 metres. One metre is about 3 3⁄8 inches longer than a yard, Metre is the standard spelling of the metric unit for length in nearly all English-speaking nations except the United States and the Philippines, which use meter. Measuring devices are spelled -meter in all variants of English, the suffix -meter has the same Greek origin as the unit of length. This range of uses is found in Latin, French, English. Thus calls for measurement and moderation. In 1668 the English cleric and philosopher John Wilkins proposed in an essay a decimal-based unit of length, as a result of the French Revolution, the French Academy of Sciences charged a commission with determining a single scale for all measures. In 1668, Wilkins proposed using Christopher Wrens suggestion of defining the metre using a pendulum with a length which produced a half-period of one second, christiaan Huygens had observed that length to be 38 Rijnland inches or 39.26 English inches. This is the equivalent of what is now known to be 997 mm, no official action was taken regarding this suggestion. In the 18th century, there were two approaches to the definition of the unit of length. One favoured Wilkins approach, to define the metre in terms of the length of a pendulum which produced a half-period of one second. The other approach was to define the metre as one ten-millionth of the length of a quadrant along the Earths meridian, that is, the distance from the Equator to the North Pole. This means that the quadrant would have defined as exactly 10000000 metres at that time. To establish a universally accepted foundation for the definition of the metre, more measurements of this meridian were needed. This portion of the meridian, assumed to be the length as the Paris meridian, was to serve as the basis for the length of the half meridian connecting the North Pole with the Equator

4.
Orders of magnitude (length)
–
The following are examples of orders of magnitude for different lengths. To help compare different orders of magnitude, the following list describes various lengths between 1. 6×10−35 meters and 101010122 meters,100 pm –1 Ångström 120 pm – radius of a gold atom 150 pm – Length of a typical covalent bond. 280 pm – Average size of the water molecule 298 pm – radius of a caesium atom, light travels 1 metre in 1⁄299,792,458, or 3. 3356409519815E-9 of a second. 25 metres – wavelength of the broadcast radio shortwave band at 12 MHz 29 metres – height of the lighthouse at Savudrija, Slovenia. 31 metres – wavelength of the broadcast radio shortwave band at 9.7 MHz 34 metres – height of the Split Point Lighthouse in Aireys Inlet, Victoria, Australia. 1 kilometre is equal to,1,000 metres 0.621371 miles 1,093.61 yards 3,280.84 feet 39,370.1 inches 100,000 centimetres 1,000,000 millimetres Side of a square of area 1 km2. Radius of a circle of area π km2,1.637 km – deepest dive of Lake Baikal in Russia, the worlds largest fresh water lake. 2.228 km – height of Mount Kosciuszko, highest point in Australia Most of Manhattan is from 3 to 4 km wide, farsang, a modern unit of measure commonly used in Iran and Turkey. Usage of farsang before 1926 may be for a precise unit derived from parasang. It is the altitude at which the FAI defines spaceflight to begin, to help compare orders of magnitude, this page lists lengths between 100 and 1,000 kilometres. 7.9 Gm – Diameter of Gamma Orionis 9, the newly improved measurement was 30% lower than the previous 2007 estimate. The size was revised in 2012 through improved measurement techniques and its faintness gives us an idea how our Sun would appear when viewed from even so close a distance as this. 350 Pm –37 light years – Distance to Arcturus 373.1 Pm –39.44 light years - Distance to TRAPPIST-1, a star recently discovered to have 7 planets around it. 400 Pm –42 light years – Distance to Capella 620 Pm –65 light years – Distance to Aldebaran This list includes distances between 1 and 10 exametres. 13 Em –1,300 light years – Distance to the Orion Nebula 14 Em –1,500 light years – Approximate thickness of the plane of the Milky Way galaxy at the Suns location 30.8568 Em –3,261. At this scale, expansion of the universe becomes significant, Distance of these objects are derived from their measured redshifts, which depends on the cosmological models used. At this scale, expansion of the universe becomes significant, Distance of these objects are derived from their measured redshifts, which depends on the cosmological models used. 590 Ym –62 billion light years – Cosmological event horizon, displays orders of magnitude in successively larger rooms Powers of Ten Travel across the Universe

5.
Electron
–
The electron is a subatomic particle, symbol e− or β−, with a negative elementary electric charge. Electrons belong to the first generation of the lepton particle family, the electron has a mass that is approximately 1/1836 that of the proton. Quantum mechanical properties of the include a intrinsic angular momentum of a half-integer value, expressed in units of the reduced Planck constant. As it is a fermion, no two electrons can occupy the same state, in accordance with the Pauli exclusion principle. Like all elementary particles, electrons exhibit properties of particles and waves, they can collide with other particles and can be diffracted like light. Since an electron has charge, it has an electric field. Electromagnetic fields produced from other sources will affect the motion of an electron according to the Lorentz force law, electrons radiate or absorb energy in the form of photons when they are accelerated. Laboratory instruments are capable of trapping individual electrons as well as electron plasma by the use of electromagnetic fields, special telescopes can detect electron plasma in outer space. Electrons are involved in applications such as electronics, welding, cathode ray tubes, electron microscopes, radiation therapy, lasers, gaseous ionization detectors. Interactions involving electrons with other particles are of interest in fields such as chemistry. The Coulomb force interaction between the positive protons within atomic nuclei and the negative electrons without, allows the composition of the two known as atoms, ionization or differences in the proportions of negative electrons versus positive nuclei changes the binding energy of an atomic system. The exchange or sharing of the electrons between two or more atoms is the cause of chemical bonding. In 1838, British natural philosopher Richard Laming first hypothesized the concept of a quantity of electric charge to explain the chemical properties of atoms. Irish physicist George Johnstone Stoney named this charge electron in 1891, electrons can also participate in nuclear reactions, such as nucleosynthesis in stars, where they are known as beta particles. Electrons can be created through beta decay of isotopes and in high-energy collisions. The antiparticle of the electron is called the positron, it is identical to the electron except that it carries electrical, when an electron collides with a positron, both particles can be totally annihilated, producing gamma ray photons. The ancient Greeks noticed that amber attracted small objects when rubbed with fur, along with lightning, this phenomenon is one of humanitys earliest recorded experiences with electricity. In his 1600 treatise De Magnete, the English scientist William Gilbert coined the New Latin term electricus, both electric and electricity are derived from the Latin ēlectrum, which came from the Greek word for amber, ἤλεκτρον

6.
Quark
–
A quark is an elementary particle and a fundamental constituent of matter. Quarks combine to form composite particles called hadrons, the most stable of which are protons and neutrons, due to a phenomenon known as color confinement, quarks are never directly observed or found in isolation, they can be found only within hadrons, such as baryons and mesons. For this reason, much of what is known about quarks has been drawn from observations of the hadrons themselves, Quarks have various intrinsic properties, including electric charge, mass, color charge, and spin. There are six types of quarks, known as flavors, up, down, strange, charm, top, up and down quarks have the lowest masses of all quarks. The heavier quarks rapidly change into up and down quarks through a process of particle decay, the transformation from a higher mass state to a lower mass state. Because of this, up and down quarks are generally stable and the most common in the universe, whereas strange, charm, bottom, and top quarks can only be produced in high energy collisions. For every quark flavor there is a type of antiparticle, known as an antiquark. The quark model was proposed by physicists Murray Gell-Mann and George Zweig in 1964. Accelerator experiments have provided evidence for all six flavors, the top quark was the last to be discovered at Fermilab in 1995. The Standard Model is the theoretical framework describing all the known elementary particles. This model contains six flavors of quarks, named up, down, strange, charm, bottom, antiparticles of quarks are called antiquarks, and are denoted by a bar over the symbol for the corresponding quark, such as u for an up antiquark. As with antimatter in general, antiquarks have the mass, mean lifetime, and spin as their respective quarks. Quarks are spin- 1⁄2 particles, implying that they are fermions according to the spin-statistics theorem and they are subject to the Pauli exclusion principle, which states that no two identical fermions can simultaneously occupy the same quantum state. This is in contrast to bosons, any number of which can be in the same state, unlike leptons, quarks possess color charge, which causes them to engage in the strong interaction. The resulting attraction between different quarks causes the formation of composite particles known as hadrons, there are two families of hadrons, baryons, with three valence quarks, and mesons, with a valence quark and an antiquark. The most common baryons are the proton and the neutron, the blocks of the atomic nucleus. A great number of hadrons are known, most of them differentiated by their quark content, the existence of exotic hadrons with more valence quarks, such as tetraquarks and pentaquarks, has been conjectured but not proven. However, on 13 July 2015, the LHCb collaboration at CERN reported results consistent with pentaquark states, elementary fermions are grouped into three generations, each comprising two leptons and two quarks

7.
String (physics)
–
In physics, a string is a physical phenomenon that appears in string theory and related subjects. Unlike elementary particles, which are zero-dimensional or point-like by definition, theories in which the fundamental objects are strings rather than point particles automatically have many properties that some physicists expect to hold in a fundamental theory of physics. Most notably, a theory of strings that evolve and interact according to the rules of quantum mechanics will automatically describe quantum gravity, in string theory, the strings may be open or closed and may have other special properties. Prior to 1995, there were five versions of string theory incorporating the idea of supersymmetry. Today these different string theories are thought to arise as different limiting cases of a theory called M-theory. Strings are also studied in nuclear physics where they are used to model flux tubes. As it propagates through spacetime, a string sweeps out a surface called its worldsheet. This is analogous to the one-dimensional worldline traced out by a point particle, the physics of a string is described by means of a two-dimensional conformal field theory associated with the worldsheet. The formalism of two dimensional conformal field theory also has applications outside of string theory, for example in condensed matter physics. Strings can be open or closed. A closed string is a string that has no end-points, an open string, on the other hand, has two end-points and is topologically equivalent to a line interval. Not all string theories contain open strings, but every theory must contain closed strings, the oldest superstring theory containing open strings was type I string theory. Open and closed strings are generally associated with characteristic vibrational modes, one of the vibration modes of a closed string can be identified as the graviton. In certain string theories the lowest-energy vibration of a string is a tachyon. Other vibrational modes of open strings exhibit the properties of photons and gluons, strings can also possess an orientation, which can be thought of as an internal arrow which distinguishes the string from one with the opposite orientation. By contrast, a string is one with no such arrow on it. Elementary particle Brane D-brane Schwarz, John

8.
Atomic nucleus
–
After the discovery of the neutron in 1932, models for a nucleus composed of protons and neutrons were quickly developed by Dmitri Ivanenko and Werner Heisenberg. Almost all of the mass of an atom is located in the nucleus, protons and neutrons are bound together to form a nucleus by the nuclear force. The diameter of the nucleus is in the range of 6985175000000000000♠1.75 fm for hydrogen to about 6986150000000000000♠15 fm for the heaviest atoms and these dimensions are much smaller than the diameter of the atom itself, by a factor of about 23,000 to about 145,000. The branch of physics concerned with the study and understanding of the nucleus, including its composition. The nucleus was discovered in 1911, as a result of Ernest Rutherfords efforts to test Thomsons plum pudding model of the atom, the electron had already been discovered earlier by J. J. Knowing that atoms are electrically neutral, Thomson postulated that there must be a charge as well. In his plum pudding model, Thomson suggested that an atom consisted of negative electrons randomly scattered within a sphere of positive charge, to his surprise, many of the particles were deflected at very large angles. This justified the idea of an atom with a dense center of positive charge. The term nucleus is from the Latin word nucleus, a diminutive of nux, in 1844, Michael Faraday used the term to refer to the central point of an atom. The modern atomic meaning was proposed by Ernest Rutherford in 1912, the adoption of the term nucleus to atomic theory, however, was not immediate. In 1916, for example, Gilbert N, the nuclear strong force extends far enough from each baryon so as to bind the neutrons and protons together against the repulsive electrical force between the positively charged protons. The nuclear strong force has a short range, and essentially drops to zero just beyond the edge of the nucleus. The collective action of the charged nucleus is to hold the electrically negative charged electrons in their orbits about the nucleus. The collection of negatively charged electrons orbiting the nucleus display an affinity for certain configurations, which chemical element an atom represents is determined by the number of protons in the nucleus, the neutral atom will have an equal number of electrons orbiting that nucleus. Individual chemical elements can create more stable electron configurations by combining to share their electrons and it is that sharing of electrons to create stable electronic orbits about the nucleus that appears to us as the chemistry of our macro world. Protons define the entire charge of a nucleus, and hence its chemical identity, neutrons are electrically neutral, but contribute to the mass of a nucleus to nearly the same extent as the protons. Neutrons explain the phenomenon of isotopes – varieties of the chemical element which differ only in their atomic mass. They are sometimes viewed as two different quantum states of the particle, the nucleon

9.
Proton
–
A proton is a subatomic particle, symbol p or p+, with a positive electric charge of +1e elementary charge and mass slightly less than that of a neutron. Protons and neutrons, each with masses of one atomic mass unit, are collectively referred to as nucleons. One or more protons are present in the nucleus of every atom, the number of protons in the nucleus is the defining property of an element, and is referred to as the atomic number. Since each element has a number of protons, each element has its own unique atomic number. The word proton is Greek for first, and this name was given to the nucleus by Ernest Rutherford in 1920. In previous years, Rutherford had discovered that the nucleus could be extracted from the nuclei of nitrogen by atomic collisions. Protons were therefore a candidate to be a particle, and hence a building block of nitrogen. In the modern Standard Model of particle physics, protons are hadrons, and like neutrons, although protons were originally considered fundamental or elementary particles, they are now known to be composed of three valence quarks, two up quarks and one down quark. The rest masses of quarks contribute only about 1% of a protons mass, the remainder of a protons mass is due to quantum chromodynamics binding energy, which includes the kinetic energy of the quarks and the energy of the gluon fields that bind the quarks together. At sufficiently low temperatures, free protons will bind to electrons, however, the character of such bound protons does not change, and they remain protons. A fast proton moving through matter will slow by interactions with electrons and nuclei, the result is a protonated atom, which is a chemical compound of hydrogen. In vacuum, when electrons are present, a sufficiently slow proton may pick up a single free electron, becoming a neutral hydrogen atom. Such free hydrogen atoms tend to react chemically with other types of atoms at sufficiently low energies. When free hydrogen atoms react with other, they form neutral hydrogen molecules. Protons are spin-½ fermions and are composed of three quarks, making them baryons. Protons have an exponentially decaying positive charge distribution with a mean square radius of about 0.8 fm. Protons and neutrons are both nucleons, which may be together by the nuclear force to form atomic nuclei. The nucleus of the most common isotope of the atom is a lone proton

10.
Neutron
–
The neutron is a subatomic particle, symbol n or n0, with no net electric charge and a mass slightly larger than that of a proton. Protons and neutrons, each with approximately one atomic mass unit, constitute the nucleus of an atom. Their properties and interactions are described by nuclear physics, the nucleus consists of Z protons, where Z is called the atomic number, and N neutrons, where N is the neutron number. The atomic number defines the properties of the atom. The terms isotope and nuclide are often used synonymously, but they are chemical and nuclear concepts, the atomic mass number, symbol A, equals Z+N. For example, carbon has atomic number 6, and its abundant carbon-12 isotope has 6 neutrons, some elements occur in nature with only one stable isotope, such as fluorine. Other elements occur with many stable isotopes, such as tin with ten stable isotopes, even though it is not a chemical element, the neutron is included in the table of nuclides. Within the nucleus, protons and neutrons are bound together through the nuclear force, neutrons are produced copiously in nuclear fission and fusion. They are a contributor to the nucleosynthesis of chemical elements within stars through fission, fusion. The neutron is essential to the production of nuclear power, in the decade after the neutron was discovered in 1932, neutrons were used to induce many different types of nuclear transmutations. These events and findings led to the first self-sustaining nuclear reactor, free neutrons, or individual neutrons free of the nucleus, are effectively a form of ionizing radiation, and as such, are a biological hazard, depending upon dose. A small natural background flux of free neutrons exists on Earth, caused by cosmic ray showers. Dedicated neutron sources like neutron generators, research reactors and spallation sources produce free neutrons for use in irradiation, neutrons and protons are both nucleons, which are attracted and bound together by the nuclear force to form atomic nuclei. The nucleus of the most common isotope of the atom is a lone proton. The nuclei of the hydrogen isotopes deuterium and tritium contain one proton bound to one. All other types of nuclei are composed of two or more protons and various numbers of neutrons. The most common nuclide of the chemical element lead, 208Pb has 82 protons and 126 neutrons. The free neutron has a mass of about 1. 675×10−27 kg, the neutron has a mean square radius of about 0. 8×10−15 m, or 0.8 fm, and it is a spin-½ fermion

11.
Picometre
–
The picometre or picometer is a unit of length in the metric system, equal to 1×10−12 m, or one trillionth of a metre, which is the SI base unit of length. The picometre is one thousandth of a nanometre, one millionth of a micrometre, the symbol µµ was once used for it. It is also one hundredth of an angstrom, a recognised unit of length. The picometres length is of an such that its application is almost entirely confined to particle physics, quantum physics, chemistry. Atoms are between 62 and 520 pm in diameter, and the length of a carbon-carbon single bond is 154 pm. Smaller units still may be used to describe smaller particles, such as hadrons and the upper limits of possible size for fermion point particles

12.
Wavelength
–
In physics, the wavelength of a sinusoidal wave is the spatial period of the wave—the distance over which the waves shape repeats, and thus the inverse of the spatial frequency. Wavelength is commonly designated by the Greek letter lambda, the concept can also be applied to periodic waves of non-sinusoidal shape. The term wavelength is also applied to modulated waves. Wavelength depends on the medium that a wave travels through, examples of wave-like phenomena are sound waves, light, water waves and periodic electrical signals in a conductor. A sound wave is a variation in air pressure, while in light and other electromagnetic radiation the strength of the electric, water waves are variations in the height of a body of water. In a crystal lattice vibration, atomic positions vary, wavelength is a measure of the distance between repetitions of a shape feature such as peaks, valleys, or zero-crossings, not a measure of how far any given particle moves. For example, in waves over deep water a particle near the waters surface moves in a circle of the same diameter as the wave height. The range of wavelengths or frequencies for wave phenomena is called a spectrum, the name originated with the visible light spectrum but now can be applied to the entire electromagnetic spectrum as well as to a sound spectrum or vibration spectrum. In linear media, any pattern can be described in terms of the independent propagation of sinusoidal components. The wavelength λ of a sinusoidal waveform traveling at constant speed v is given by λ = v f, in a dispersive medium, the phase speed itself depends upon the frequency of the wave, making the relationship between wavelength and frequency nonlinear. In the case of electromagnetic radiation—such as light—in free space, the speed is the speed of light. Thus the wavelength of a 100 MHz electromagnetic wave is about, the wavelength of visible light ranges from deep red, roughly 700 nm, to violet, roughly 400 nm. For sound waves in air, the speed of sound is 343 m/s, the wavelengths of sound frequencies audible to the human ear are thus between approximately 17 m and 17 mm, respectively. Note that the wavelengths in audible sound are much longer than those in visible light, a standing wave is an undulatory motion that stays in one place. A sinusoidal standing wave includes stationary points of no motion, called nodes, the upper figure shows three standing waves in a box. The walls of the box are considered to require the wave to have nodes at the walls of the box determining which wavelengths are allowed, the stationary wave can be viewed as the sum of two traveling sinusoidal waves of oppositely directed velocities. Consequently, wavelength, period, and wave velocity are related just as for a traveling wave, for example, the speed of light can be determined from observation of standing waves in a metal box containing an ideal vacuum. In that case, the k, the magnitude of k, is still in the same relationship with wavelength as shown above

13.
Gamma ray
–
Gamma ray, denoted by the lower-case Greek letter gamma, is penetrating electromagnetic radiation of a kind arising from the radioactive decay of atomic nuclei. It consists of photons in the highest observed range of photon energy, paul Villard, a French chemist and physicist, discovered gamma radiation in 1900 while studying radiation emitted by radium. In 1903, Ernest Rutherford named this radiation gamma rays, Rutherford had previously discovered two other types of radioactive decay, which he named alpha and beta rays. Gamma rays are able to ionize atoms, and are thus biologically hazardous. The decay of a nucleus from a high energy state to a lower energy state. Natural sources of gamma rays on Earth are observed in the decay of radionuclides. There are rare terrestrial natural sources, such as lightning strikes and terrestrial gamma-ray flashes, However, a large fraction of such astronomical gamma rays are screened by Earths atmosphere and can only be detected by spacecraft. Gamma rays typically have frequencies above 10 exahertz, and therefore have energies above 100 keV and wavelengths less than 10 picometers, However, this is not a strict definition, but rather only a rule-of-thumb description for natural processes. Electromagnetic radiation from radioactive decay of nuclei is referred to as gamma rays no matter its energy. This radiation commonly has energy of a few hundred keV, in astronomy, gamma rays are defined by their energy, and no production process needs to be specified. The energies of gamma rays from astronomical sources range to over 10 TeV, a notable example is the extremely powerful bursts of high-energy radiation referred to as long duration gamma-ray bursts, of energies higher than can be produced by radioactive decay. These bursts of gamma rays are thought to be due to the collapse of stars called hypernovae, the first gamma ray source to be discovered historically was the radioactive decay process called gamma decay. In this type of decay, a nucleus emits a gamma ray almost immediately upon formation. Paul Villard, a French chemist and physicist, discovered gamma radiation in 1900, However, Villard did not consider naming them as a different fundamental type. Rutherford also noted that gamma rays were not deflected by a field, another property making them unlike alpha. Gamma rays were first thought to be particles with mass, like alpha, Rutherford initially believed that they might be extremely fast beta particles, but their failure to be deflected by a magnetic field indicated that they had no charge. In 1914, gamma rays were observed to be reflected from crystal surfaces, Rutherford and his coworker Edward Andrade measured the wavelengths of gamma rays from radium, and found that they were similar to X-rays, but with shorter wavelengths and higher frequency. This was eventually recognized as giving them more energy per photon

14.
X-ray
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X-radiation is a form of electromagnetic radiation. Most X-rays have a wavelength ranging from 0.01 to 10 nanometers, corresponding to frequencies in the range 30 petahertz to 30 exahertz, X-ray wavelengths are shorter than those of UV rays and typically longer than those of gamma rays. Spelling of X-ray in the English language includes the variants x-ray, xray, X-rays with high photon energies are called hard X-rays, while those with lower energy are called soft X-rays. Due to their ability, hard X-rays are widely used to image the inside of objects, e. g. in medical radiography. The term X-ray is metonymically used to refer to an image produced using this method. Since the wavelengths of hard X-rays are similar to the size of atoms they are useful for determining crystal structures by X-ray crystallography. By contrast, soft X-rays are easily absorbed in air, the length of 600 eV X-rays in water is less than 1 micrometer. There is no consensus for a definition distinguishing between X-rays and gamma rays, one common practice is to distinguish between the two types of radiation based on their source, X-rays are emitted by electrons, while gamma rays are emitted by the atomic nucleus. This definition has problems, other processes also can generate these high-energy photons. One common alternative is to distinguish X- and gamma radiation on the basis of wavelength, with radiation shorter than some arbitrary wavelength, such as 10−11 m and this criterion assigns a photon to an unambiguous category, but is only possible if wavelength is known. Occasionally, one term or the other is used in specific contexts due to precedent, based on measurement technique. Thus, gamma-rays generated for medical and industrial uses, for radiotherapy, in the ranges of 6–20 MeV. X-ray photons carry enough energy to ionize atoms and disrupt molecular bonds and this makes it a type of ionizing radiation, and therefore harmful to living tissue. A very high radiation dose over a period of time causes radiation sickness. In medical imaging this increased risk is generally greatly outweighed by the benefits of the examination. The ionizing capability of X-rays can be utilized in treatment to kill malignant cells using radiation therapy. It is also used for material characterization using X-ray spectroscopy, hard X-rays can traverse relatively thick objects without being much absorbed or scattered. For this reason, X-rays are widely used to image the inside of visually opaque objects, the most often seen applications are in medical radiography and airport security scanners, but similar techniques are also important in industry and research

15.
Hydrogen
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Hydrogen is a chemical element with chemical symbol H and atomic number 1. With a standard weight of circa 1.008, hydrogen is the lightest element on the periodic table. Its monatomic form is the most abundant chemical substance in the Universe, non-remnant stars are mainly composed of hydrogen in the plasma state. The most common isotope of hydrogen, termed protium, has one proton, the universal emergence of atomic hydrogen first occurred during the recombination epoch. At standard temperature and pressure, hydrogen is a colorless, odorless, tasteless, non-toxic, nonmetallic, since hydrogen readily forms covalent compounds with most nonmetallic elements, most of the hydrogen on Earth exists in molecular forms such as water or organic compounds. Hydrogen plays an important role in acid–base reactions because most acid-base reactions involve the exchange of protons between soluble molecules. In ionic compounds, hydrogen can take the form of a charge when it is known as a hydride. The hydrogen cation is written as though composed of a bare proton, Hydrogen gas was first artificially produced in the early 16th century by the reaction of acids on metals. Industrial production is mainly from steam reforming natural gas, and less often from more energy-intensive methods such as the electrolysis of water. Most hydrogen is used near the site of its production, the two largest uses being fossil fuel processing and ammonia production, mostly for the fertilizer market, Hydrogen is a concern in metallurgy as it can embrittle many metals, complicating the design of pipelines and storage tanks. Hydrogen gas is flammable and will burn in air at a very wide range of concentrations between 4% and 75% by volume. The enthalpy of combustion is −286 kJ/mol,2 H2 + O2 →2 H2O +572 kJ Hydrogen gas forms explosive mixtures with air in concentrations from 4–74%, the explosive reactions may be triggered by spark, heat, or sunlight. The hydrogen autoignition temperature, the temperature of spontaneous ignition in air, is 500 °C, the detection of a burning hydrogen leak may require a flame detector, such leaks can be very dangerous. Hydrogen flames in other conditions are blue, resembling blue natural gas flames, the destruction of the Hindenburg airship was a notorious example of hydrogen combustion and the cause is still debated. The visible orange flames in that incident were the result of a mixture of hydrogen to oxygen combined with carbon compounds from the airship skin. H2 reacts with every oxidizing element, the ground state energy level of the electron in a hydrogen atom is −13.6 eV, which is equivalent to an ultraviolet photon of roughly 91 nm wavelength. The energy levels of hydrogen can be calculated fairly accurately using the Bohr model of the atom, however, the atomic electron and proton are held together by electromagnetic force, while planets and celestial objects are held by gravity. The most complicated treatments allow for the effects of special relativity

16.
DNA
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Deoxyribonucleic acid is a molecule that carries the genetic instructions used in the growth, development, functioning and reproduction of all known living organisms and many viruses. DNA and RNA are nucleic acids, alongside proteins, lipids and complex carbohydrates, most DNA molecules consist of two biopolymer strands coiled around each other to form a double helix. The two DNA strands are termed polynucleotides since they are composed of simpler units called nucleotides. Each nucleotide is composed of one of four nitrogen-containing nucleobases—cytosine, guanine, adenine, or thymine —a sugar called deoxyribose, and a phosphate group. The nucleotides are joined to one another in a chain by covalent bonds between the sugar of one nucleotide and the phosphate of the next, resulting in an alternating sugar-phosphate backbone. The nitrogenous bases of the two polynucleotide strands are bound together, according to base pairing rules, with hydrogen bonds to make double-stranded DNA. The total amount of related DNA base pairs on Earth is estimated at 5.0 x 1037, in comparison the total mass of the biosphere has been estimated to be as much as 4 trillion tons of carbon. The DNA backbone is resistant to cleavage, and both strands of the double-stranded structure store the same biological information and this information is replicated as and when the two strands separate. A large part of DNA is non-coding, meaning that these sections do not serve as patterns for protein sequences, the two strands of DNA run in opposite directions to each other and are thus antiparallel. Attached to each sugar is one of four types of nucleobases and it is the sequence of these four nucleobases along the backbone that encodes biological information. RNA strands are created using DNA strands as a template in a process called transcription, under the genetic code, these RNA strands are translated to specify the sequence of amino acids within proteins in a process called translation. Within eukaryotic cells DNA is organized into structures called chromosomes. During cell division these chromosomes are duplicated in the process of DNA replication, eukaryotic organisms store most of their DNA inside the cell nucleus and some of their DNA in organelles, such as mitochondria or chloroplasts. In contrast prokaryotes store their DNA only in the cytoplasm, within the eukaryotic chromosomes, chromatin proteins such as histones compact and organize DNA. These compact structures guide the interactions between DNA and other proteins, helping control which parts of the DNA are transcribed, DNA was first isolated by Friedrich Miescher in 1869. DNA is used by researchers as a tool to explore physical laws and theories, such as the ergodic theorem. The unique material properties of DNA have made it an attractive molecule for material scientists and engineers interested in micro-, among notable advances in this field are DNA origami and DNA-based hybrid materials. DNA is a polymer made from repeating units called nucleotides

17.
Helix
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A helix is a type of smooth space curve, i. e. a curve in three-dimensional space. It has the property that the tangent line at any point makes a constant angle with a line called the axis. Examples of helices are coil springs and the handrails of spiral staircases, a filled-in helix – for example, a spiral ramp – is called a helicoid. Helices are important in biology, as the DNA molecule is formed as two intertwined helices, and many proteins have helical substructures, known as alpha helices, the word helix comes from the Greek word ἕλιξ, twisted, curved. Helices can be either right-handed or left-handed, handedness is a property of the helix, not of the perspective, a right-handed helix cannot be turned to look like a left-handed one unless it is viewed in a mirror, and vice versa. Most hardware screw threads are right-handed helices, the alpha helix in biology as well as the A and B forms of DNA are also right-handed helices. The Z form of DNA is left-handed, the pitch of a helix is the height of one complete helix turn, measured parallel to the axis of the helix. A double helix consists of two helices with the axis, differing by a translation along the axis. A conic helix may be defined as a spiral on a conic surface, an example is the Corkscrew roller coaster at Cedar Point amusement park. A circular helix, has constant band curvature and constant torsion, a curve is called a general helix or cylindrical helix if its tangent makes a constant angle with a fixed line in space. A curve is a general helix if and only if the ratio of curvature to torsion is constant, a curve is called a slant helix if its principal normal makes a constant angle with a fixed line in space. It can be constructed by applying a transformation to the frame of a general helix. Some curves found in nature consist of multiple helices of different handedness joined together by transitions known as tendril perversions, in mathematics, a helix is a curve in 3-dimensional space. The following parametrisation in Cartesian coordinates defines a particular helix, Probably the simplest equations for one is x = cos ⁡, y = sin ⁡, z = t. As the parameter t increases, the point traces a right-handed helix of pitch 2θ and radius 1 about the z-axis, in cylindrical coordinates, the same helix is parametrised by, r =1, θ = t, h = t. A circular helix of radius a and slope b/a is described by the following parametrisation, another way of mathematically constructing a helix is to plot the complex-valued function exi as a function of the real number x. The value of x and the real and imaginary parts of the function value give this plot three real dimensions, except for rotations, translations, and changes of scale, all right-handed helices are equivalent to the helix defined above. The equivalent left-handed helix can be constructed in a number of ways, in music, pitch space is often modeled with helices or double helices, most often extending out of a circle such as the circle of fifths, so as to represent octave equivalency

18.
Visible spectrum
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The visible spectrum is the portion of the electromagnetic spectrum that is visible to the human eye. Electromagnetic radiation in this range of wavelengths is called light or simply light. A typical human eye will respond to wavelengths from about 390 to 700 nm, in terms of frequency, this corresponds to a band in the vicinity of 430–770 THz. The spectrum does not, however, contain all the colors that the human eyes, unsaturated colors such as pink, or purple variations such as magenta, are absent, for example, because they can be made only by a mix of multiple wavelengths. Colors containing only one wavelength are called pure colors or spectral colors. Visible wavelengths pass through the window, the region of the electromagnetic spectrum that allows wavelengths to pass largely unattenuated through the Earths atmosphere. An example of this phenomenon is that clean air scatters blue light more than red wavelengths, the optical window is also referred to as the visible window because it overlaps the human visible response spectrum. The near infrared window lies just out of the vision, as well as the Medium Wavelength IR window. In the 13th century, Roger Bacon theorized that rainbows were produced by a process to the passage of light through glass or crystal. In the 17th century, Isaac Newton discovered that prisms could disassemble and reassemble white light and he was the first to use the word spectrum in this sense in print in 1671 in describing his experiments in optics. The result is red light is bent less sharply than violet as it passes through the prism. Newton divided the spectrum into seven named colors, red, orange, yellow, green, blue, indigo, the human eye is relatively insensitive to indigos frequencies, and some people who have otherwise-good vision cannot distinguish indigo from blue and violet. For this reason, some commentators, including Isaac Asimov, have suggested that indigo should not be regarded as a color in its own right. However, the evidence indicates that what Newton meant by indigo, comparing Newtons observation of prismatic colors to a color image of the visible light spectrum shows that indigo corresponds to what is today called blue, whereas blue corresponds to cyan. In the 18th century, Goethe wrote about optical spectra in his Theory of Colours, Goethe used the word spectrum to designate a ghostly optical afterimage, as did Schopenhauer in On Vision and Colors. Goethe argued that the spectrum was a compound phenomenon. Where Newton narrowed the beam of light to isolate the phenomenon, Goethe observed that a wider aperture produces not a spectrum but rather reddish-yellow, the spectrum appears only when these edges are close enough to overlap. Young was the first to measure the wavelengths of different colors of light, the connection between the visible spectrum and color vision was explored by Thomas Young and Hermann von Helmholtz in the early 19th century

19.
Bacterium
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Bacteria constitute a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria have a number of shapes, ranging from spheres to rods, Bacteria were among the first life forms to appear on Earth, and are present in most of its habitats. Bacteria inhabit soil, water, acidic hot springs, radioactive waste, Bacteria also live in symbiotic and parasitic relationships with plants and animals. Most bacteria have not been characterised, and only half of the bacterial phyla have species that can be grown in the laboratory. The study of bacteria is known as bacteriology, a branch of microbiology, There are typically 40 million bacterial cells in a gram of soil and a million bacterial cells in a millilitre of fresh water. There are approximately 5×1030 bacteria on Earth, forming a biomass which exceeds that of all plants, Bacteria are vital in many stages of the nutrient cycle by recycling nutrients such as the fixation of nitrogen from the atmosphere. The nutrient cycle includes the decomposition of bodies and bacteria are responsible for the putrefaction stage in this process. In March 2013, data reported by researchers in October 2012, was published and it was suggested that bacteria thrive in the Mariana Trench, which with a depth of up to 11 kilometres is the deepest known part of the oceans. Other researchers reported related studies that microbes thrive inside rocks up to 580 metres below the sea floor under 2.6 kilometres of ocean off the coast of the northwestern United States. According to one of the researchers, You can find microbes everywhere—theyre extremely adaptable to conditions, the vast majority of the bacteria in the body are rendered harmless by the protective effects of the immune system, though many are beneficial particularly in the gut flora. However several species of bacteria are pathogenic and cause diseases, including cholera, syphilis, anthrax, leprosy. The most common fatal diseases are respiratory infections, with tuberculosis alone killing about 2 million people per year. In developed countries, antibiotics are used to treat infections and are also used in farming, making antibiotic resistance a growing problem. Once regarded as constituting the class Schizomycetes, bacteria are now classified as prokaryotes. Unlike cells of animals and other eukaryotes, bacterial cells do not contain a nucleus and these evolutionary domains are called Bacteria and Archaea. The ancestors of modern bacteria were unicellular microorganisms that were the first forms of life to appear on Earth, for about 3 billion years, most organisms were microscopic, and bacteria and archaea were the dominant forms of life. In 2008, fossils of macroorganisms were discovered and named as the Francevillian biota, however, gene sequences can be used to reconstruct the bacterial phylogeny, and these studies indicate that bacteria diverged first from the archaeal/eukaryotic lineage. Bacteria were also involved in the second great evolutionary divergence, that of the archaea, here, eukaryotes resulted from the entering of ancient bacteria into endosymbiotic associations with the ancestors of eukaryotic cells, which were themselves possibly related to the Archaea

20.
Fog
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Fog consists of visible cloud water droplets or ice crystals suspended in the air at or near the Earths surface. Fog can be considered a type of low-lying cloud and is influenced by nearby bodies of water, topography. In turn, fog has affected many human activities, such as shipping, travel, the term fog is typically distinguished from the more generic term cloud in that fog is low-lying, and the moisture in the fog is often generated locally. By definition, fog reduces visibility to less than 1 kilometre, for aviation purposes in the UK, a visibility of less than 5 kilometres but greater than 999 metres is considered to be mist if the relative humidity is 70% or greater, below 70%, haze is reported. Fog forms when the difference between air temperature and dew point is less than 2.5 °C or 4 °F, Fog begins to form when water vapor condenses into tiny liquid water droplets suspended in the air. Water vapor normally begins to condense on condensation nuclei such as dust, ice, Fog, like its elevated cousin stratus, is a stable cloud deck which tends to form when a cool, stable air mass is trapped underneath a warm air mass. Fog normally occurs at a relative humidity near 100% and this occurs from either added moisture in the air, or falling ambient air temperature. However, fog can form at lower humidities, and can fail to form with relative humidity at 100%. At 100% relative humidity, the air cannot hold additional moisture, thus, Fog can form suddenly and can dissipate just as rapidly. The sudden formation of fog is known as flash fog, Fog commonly produces precipitation in the form of drizzle or very light snow. Drizzle occurs when the humidity of fog attains 100% and the cloud droplets begin to coalesce into larger droplets. This can occur when the fog layer is lifted and cooled sufficiently, drizzle becomes freezing drizzle when the temperature at the surface drops below the freezing point. The inversion boundary varies its altitude primarily in response to the weight of the air above it, the marine layer, and any fogbank it may contain, will be squashed when the pressure is high, and conversely, may expand upwards when the pressure above it is lowering. Fog can form in a number of ways, depending on how the cooling that caused the condensation occurred, radiation fog is formed by the cooling of land after sunset by thermal radiation in calm conditions with clear sky. The warm ground produces condensation in the air by heat conduction. In perfect calm the fog layer can be less than a meter deep, radiation fogs occur at night, and usually do not last long after sunrise, but they can persist all day in the winter months especially in areas bounded by high ground. Radiation fog is most common in autumn and early winter, examples of this phenomenon include the Tule fog. Ground fog is fog that obscures less than 60% of the sky, advection fog occurs when moist air passes over a cool surface by advection and is cooled

21.
Mosquito
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Mosquitoes are small, midge-like flies that constitute the family Culicidae. Females of most species are ectoparasites, whose tube-like mouthparts pierce the skin to consume blood. The word mosquito is Spanish for little fly, thousands of species feed on the blood of various kinds of hosts, mainly vertebrates, including mammals, birds, reptiles, amphibians, and even some kinds of fish. Some mosquitoes also attack invertebrates, mainly other arthropods, though the loss of blood is seldom of any importance to the victim, the saliva of the mosquito often causes an irritating rash that is a serious nuisance. Much more serious though, are the roles of species of mosquitoes as vectors of diseases. The oldest known mosquito with a similar to modern species was found in 79-million-year-old Canadian amber from the Cretaceous. An older sister species with more primitive features was found in Burmese amber that is 90 to 100 million years old, two mosquito fossils have been found that show very little morphological change in modern mosquitoes against their counterpart from 46 million years ago. These fossils are also the oldest ever found to have blood preserved within their abdomens, the Old and New World Anopheles species are believed to have subsequently diverged about 95 million years ago. The mosquito Anopheles gambiae is currently undergoing speciation into the M and S molecular forms, consequently, some pesticides that work on the M form no longer work on the S form. Over 3,500 species of the Culicidae have already been described and they are generally divided into two subfamilies which in turn comprise some 43 genera. These figures are subject to change, as more species are discovered. The two main subfamilies are the Anophelinae and Culicinae, with their genera as shown in the subsection below, the distinction is of great practical importance because the two subfamilies tend to differ in their significance as vectors of different classes of diseases. Roughly speaking, arboviral diseases such as fever and dengue fever tend to be transmitted by Culicine species. Some transmit various species of malaria, but it is not clear that they ever transmit any form of human malaria. Some species do however transmit various forms of filariasis, much as many Simuliidae do, Anopheline mosquitoes, again not necessarily in the genus Anopheles, sometimes bear pathogenic arboviruses, but it is not yet clear that they ever transmit them as effective vectors. However, all the most important vectors of malaria are Anopheline. Anophelinae Culicinae Mosquitoes are members of a family of nematocerid flies, superficially, mosquitoes resemble crane flies and chironomid flies. In particular, the females of species of mosquitoes are blood-eating pests and dangerous vectors of diseases

22.
Golf ball
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A golf ball is a special ball designed to be used in the game of golf. Under the rules of golf, a ball has a mass no more than 1.620 oz, has a diameter not less than 1.680 in, and performs within specified velocity, distance. Like golf clubs, golf balls are subject to testing and approval by the R&A and the United States Golf Association, and it is commonly believed that hard wooden, round balls were the first balls used for golf between the 14th through the 17th centuries. It is equally, if not more likely, that leather balls filled with cows hair were used, imported from The Netherlands from at least 1486 onwards, then or later, the featherie ball was developed and introduced. A featherie, or feathery, is a round leather pouch stuffed with chicken or goose feathers and coated with paint. The volume measurement for the feathers was a top hat full of feathers. The feathers were boiled and softened before they were stuffed into the leather pouch, making a featherie was a tedious and time-consuming process. An experienced ball maker could only make a few balls in one day, a single ball would cost between 2 shillings and 5 shillings, which is the equivalent of 10 to 20 US dollars today. There were a few drawbacks to the featherie, first, it was hard to make a perfectly round, spherical ball, and because of this, the featherie often flew irregularly. Also, when the featherie became too wet, its distance would be reduced, despite these, the featherie was still a dramatic improvement over the wooden ball, and remained the standard golf ball well into the 19th century. In 1848, the Rev. Dr. Robert Adams Paterson invented the gutta-percha ball, the guttie was made from dried sap of the Malaysian sapodilla tree. The sap had a feel and could be made round by heating and shaping it in a round mold. Because gutties were cheaper to produce, could be re-formed if they became out-of-round or damaged, accidentally, it was discovered that nicks in the guttie from normal use actually provided a ball with a more consistent ball flight than a guttie with a perfectly smooth surface. Thus, makers began intentionally making indentations into the surface of new balls using either a knife or hammer and chisel, many patterns were tried and used. These new gutties, with protruding nubs left by carving patterned paths across the balls surface, the next breakthrough in golf ball development came in 1898. Coburn Haskell of Cleveland, Ohio had driven to nearby Akron, Ohio for a date with Bertram Work. While he waited in the plant for Work, Haskell picked up some rubber thread, when he bounced the ball, it flew almost to the ceiling. Work suggested Haskell put a cover on the creation, and that was the birth of the 20th century wound golf ball that would replace the guttie bramble ball

23.
Cat
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The domestic cat is a small, typically furry, carnivorous mammal. They are often called house cats when kept as pets or simply cats when there is no need to distinguish them from other felids. Cats are often valued by humans for companionship and for their ability to hunt vermin, there are more than 70 cat breeds, though different associations proclaim different numbers according to their standards. Cats are similar in anatomy to the felids, with a strong flexible body, quick reflexes, sharp retractable claws. Cat senses fit a crepuscular and predatory ecological niche, cats can hear sounds too faint or too high in frequency for human ears, such as those made by mice and other small animals. They can see in near darkness, like most other mammals, cats have poorer color vision and a better sense of smell than humans. Cats, despite being solitary hunters, are a species and cat communication includes the use of a variety of vocalizations. Cats have a high breeding rate, under controlled breeding, they can be bred and shown as registered pedigree pets, a hobby known as cat fancy. Failure to control the breeding of pet cats by neutering, as well as the abandonment of former household pets, has resulted in numbers of feral cats worldwide. In certain areas outside cats native range, this has contributed, along with destruction and other factors. Cats have been known to extirpate a bird species within specific regions, a genetic study in 2007 concluded that domestic cats are descended from Near Eastern wildcats, having diverged around 8,000 BC in the Middle East. As of a 2007 study, cats are the second most popular pet in the US by number of pets owned, in a 2010 study they were ranked the third most popular pet in the UK, after fish and dogs, with around 8 million being owned. The domestic cat is believed to have evolved from the Near Eastern wildcat, the felids are a rapidly evolving family of mammals that share a common ancestor only 10–15 million years ago and include lions, tigers, cougars and many others. Within this family, domestic cats are part of the genus Felis, members of the genus are found worldwide and include the jungle cat of southeast Asia, European wildcat, African wildcat, the Chinese mountain cat, and the Arabian sand cat, among others. The domestic cat was first classified as Felis catus by Carl Linnaeus in the 10th edition of his Systema Naturae published in 1758, because of modern phylogenetics, domestic cats are usually regarded as another subspecies of the wildcat, F. silvestris. This has resulted in mixed usage of the terms, as the cat can be called by its subspecies name. Wildcats have also referred to as various subspecies of F. catus, but in 2003. The most common name in use for the cat remains F. catus

24.
Violin
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The violin is a wooden string instrument in the violin family. It is the smallest and highest-pitched instrument in the family in regular use, smaller violin-type instruments are known, including the violino piccolo and the kit violin, but these are virtually unused in the 2010s. The violin typically has four strings tuned in fifths, and is most commonly played by drawing a bow across its strings. Violins are important instruments in a variety of musical genres. They are most prominent in the Western classical tradition and in varieties of folk music. They are also used in genres of folk including country music and bluegrass music. Electric violins are used in forms of rock music, further. The violin is sometimes called a fiddle, particularly in Irish traditional music and bluegrass. The violin was first known in 16th-century Italy, with further modifications occurring in the 18th and 19th centuries. In Europe it served as the basis for stringed instruments used in classical music, the viola. According to their reputation, the quality of their sound has defied attempts to explain or equal it, many of these trade instruments were formerly sold by Sears, Roebuck and Co. and other mass merchandisers. A person who makes or repairs violins is called a luthier or violinmaker, the parts of a violin are usually made from different types of wood and on the use of a pickup and an amplifier and speaker). Violins can be strung with gut, Perlon or other synthetic, the earliest stringed instruments were mostly plucked. Similar and variant types were probably disseminated along East-West trading routes from Asia into the Middle East, the first makers of violins probably borrowed from various developments of the Byzantine lira. These included the rebec, the Arabic rebab, the vielle, the earliest pictures of violins, albeit with three strings, are seen in northern Italy around 1530, at around the same time as the words violino and vyollon are seen in Italian and French documents. One of the earliest explicit descriptions of the instrument, including its tuning, is from the Epitome musical by Jambe de Fer, by this time, the violin had already begun to spread throughout Europe. The violin proved very popular, both among street musicians and the nobility, the French king Charles IX ordered Andrea Amati to construct 24 violins for him in 1560, one of these noble instruments, the Charles IX, is the oldest surviving violin. The Messiah or Le Messie made by Antonio Stradivari in 1716 remains pristine and it is now located in the Ashmolean Museum of Oxford

25.
Viola
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The viola is a string instrument that is bowed or played with varying techniques. It is slightly larger than a violin and has a lower and deeper sound. Since the 18th century it has been the middle or alto voice of the family, between the violin and the cello. The strings from low to high are generally tuned to C3, G3, D4. In the past, the viola varied in size and style as did its names, the Italians often used the term, viola da braccio meaning literally, of the arm. Brazzo was another Italian word referring to the viola which the Germans adopted in the form, the French had their own names, Cinquiesme was a small viola, Haute Contre was a large viola and Taile meant Tenor. In the modern era, the French use the term Alto, the viola had enjoyed popularity in the heyday of five-part harmony up until the eighteenth century, taking three lines of the harmony and occasionally playing the melody line. Music that is written for the viola differs from that of most other instruments in that it uses the alto clef. Viola music switches to the treble clef when there are sections of music written in a higher register to make the notes easier to read. The viola often plays the voices in string quartets and symphonic writing. The viola occasionally plays a major, soloistic role in orchestral music, examples include Don Quixote by Richard Strauss and Harold en Italie by Hector Berlioz. In the earlier part of the 20th century, more composers began to write for the viola, encouraged by the emergence of specialized soloists such as Lionel Tertis and William Primrose. English composers Arthur Bliss, York Bowen, Benjamin Dale, Frank Bridge, Benjamin Britten and Ralph Vaughan Williams all wrote substantial chamber, many of these pieces were commissioned by, or written for Lionel Tertis. William Walton, Bohuslav Martinů, Toru Takemitsu, Tibor Serly, Alfred Schnittke, Paul Hindemith wrote a substantial amount of music for viola, including the concerto Der Schwanendreher. The concerti by Paul Hindemith, Béla Bartók, and William Walton are the big three of viola repertoire, the viola is similar in material and construction to the violin. A full-size violas body is between 25 mm and 100 mm longer than the body of a violin, with an average length of 41 cm. Small violas typically made for children typically start at 30 cm, for a child who needs a smaller size, a fractional-sized violin is often strung with the strings of a viola. Unlike the violin, the viola does not have a full size. The body of a viola would need to measure about 51 cm long to match the acoustics of a violin, there have been several experiments intended to increase the size of the viola, in the interest of improving the instruments sound

26.
Ball (association football)
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A football, soccer ball, or association football ball is the ball used in the sport of association football. The name of the ball according to whether the sport is called football, soccer. The balls spherical shape, as well as its size, weight, additional, more stringent, standards are specified by FIFA and subordinate governing bodies for the balls used in the competitions they sanction. Early footballs began as animal bladders or stomachs that would fall apart if kicked too much. Improvements became possible in the 19th century with the introduction of rubber, the modern 32-panel ball design was developed in 1962 by Eigil Nielsen, and technological research continues today to develop footballs with improved performance. In 1863, the first specifications for footballs were laid down by the Football Association, previous to this, footballs were made out of inflated leather, with later leather coverings to help footballs maintain their shapes. In 1872 the specifications were revised, and these rules have been essentially unchanged as defined by the International Football Association Board. Differences in footballs created since this rule came into effect have been to do with the used in their creation. Footballs have gone through a change over time. During medieval times balls were made from an outer shell of leather filled with cork shavings. Another method of creating a ball was using animal bladders for the inside of the making it inflatable. However, these two styles of creating footballs made it easy for the ball to puncture and were inadequate for kicking and it was not until the 19th century that footballs developed into what a football looks like today. In 1838, Charles Goodyear introduced the use of rubber and their discoveries of vulcanisation, Vulcanization is the treatment of rubber to give it certain qualities such as strength, elasticity, and resistance to solvents. Vulcanization of rubber also helps the football resist moderate heat and cold, Vulcanization helped create inflatable bladders that pressurise the outer panel arrangement of the football. Charles Goodyears innovation increased the ability of the ball and made it easier to kick. Most of the balls of this time had tanned leather with eighteen sections stitched together and these were arranged in six panels of three strips each. During the 1900s, footballs were made out of rubber and leather which was perfect for bouncing and kicking the ball, however, when heading the football it was usually painful. This problem was most probably due to absorption of the leather from rain

27.
Cello
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The cello or violoncello is a bowed or plucked string instrument with four strings tuned in perfect fifths. The strings from low to high are generally tuned to C2, G2, D3 and A3 and it is a member of the violin family of musical instruments, which also includes the violin and viola and the double bass. The cello is used as a musical instrument, as well as in chamber music ensembles, string orchestras, as a member of the string section of symphony orchestras. It is the second-largest and second lowest bowed string instrument in the symphony orchestra. Cello parts are written in the bass clef, but both tenor clef and treble clefs are used for higher-range parts, both in orchestral/chamber music parts and in solo cello works. A person who plays the cello is called a cellist or violoncellist, in a small Classical ensemble, such as a string quartet, the cello typically plays the bass part, the lowest-pitched musical line of the piece. In orchestra, in Baroque era and Classical music period, the cello plays the bass part. In Baroque era music, the cello is used to play the basso continuo bassline, in a Baroque performance, the cello player might be joined by other bass instruments, playing double bass, viol or other low-register instruments. The name cello is a contraction of the Italian violoncello, which means little violone, in modern symphony orchestras, it is the second largest stringed instrument. Thus, the name contained both the augmentative -one and the diminutive -cello. By the turn of the 20th century, it had become common to shorten the name to cello and it is now customary to use cello without apostrophe as the full designation. Viol is derived from the viola, which was derived from Medieval Latin vitula. Cellos are tuned in fifths, starting with C2, followed by G2, D3 and it is tuned in the same intervals as the viola, but an octave lower. Unlike the violin or viola but similar to the double bass, the cello is most closely associated with European classical music, and has been described as the closest sounding instrument to the human voice. The instrument is a part of the orchestra, as part of the string section. A large number of concertos and sonatas have been written for the cello, among the most well-known Baroque works for the cello are Johann Sebastian Bachs six unaccompanied Suites. The Prelude from the First Suite is particularly famous, romantic era repertoire includes the Robert Schumann Concerto, the Antonín Dvořák Concerto as well as the two sonatas and the Double Concerto by Johannes Brahms. The cello is increasingly common in traditional music, especially Scottish fiddle music

28.
Piano
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The piano is an acoustic, stringed musical instrument invented around the year 1700, in which the strings are struck by hammers. It is played using a keyboard, which is a row of keys that the performer presses down or strikes with the fingers and thumbs of both hands to cause the hammers to strike the strings. The word piano is a form of pianoforte, the Italian term for the early 1700s versions of the instrument. The first fortepianos in the 1700s had a sound and smaller dynamic range. An acoustic piano usually has a wooden case surrounding the soundboard and metal strings. Pressing one or more keys on the keyboard causes a padded hammer to strike the strings. The hammer rebounds from the strings, and the continue to vibrate at their resonant frequency. These vibrations are transmitted through a bridge to a soundboard that amplifies by more efficiently coupling the acoustic energy to the air, when the key is released, a damper stops the strings vibration, ending the sound. Notes can be sustained, even when the keys are released by the fingers and thumbs and this means that the piano can play 88 different pitches, going from the deepest bass range to the highest treble. The black keys are for the accidentals, which are needed to play in all twelve keys, more rarely, some pianos have additional keys. Most notes have three strings, except for the bass that graduates from one to two, the strings are sounded when keys are pressed or struck, and silenced by dampers when the hands are lifted from the keyboard. There are two types of piano, the grand piano and the upright piano. The grand piano is used for Classical solos, chamber music and art song and it is used in jazz. The upright piano, which is compact, is the most popular type, as they are a better size for use in private homes for domestic music-making. During the nineteenth century, music publishers produced many works in arrangements for piano, so that music lovers could play. The piano is widely employed in classical, jazz, traditional and popular music for solo and ensemble performances, accompaniment, with technological advances, amplified electric pianos, electronic pianos, and digital pianos have also been developed. The electric piano became an instrument in the 1960s and 1970s genres of jazz fusion, funk music. The piano was founded on earlier technological innovations in keyboard instruments, pipe organs have been used since Antiquity, and as such, the development of pipe organs enabled instrument builders to learn about creating keyboard mechanisms for sounding pitches

29.
Human
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Modern humans are the only extant members of Hominina tribe, a branch of the tribe Hominini belonging to the family of great apes. Several of these hominins used fire, occupied much of Eurasia and they began to exhibit evidence of behavioral modernity around 50,000 years ago. In several waves of migration, anatomically modern humans ventured out of Africa, the spread of humans and their large and increasing population has had a profound impact on large areas of the environment and millions of native species worldwide. Humans are uniquely adept at utilizing systems of communication for self-expression and the exchange of ideas. Humans create complex structures composed of many cooperating and competing groups, from families. Social interactions between humans have established a wide variety of values, social norms, and rituals. These human societies subsequently expanded in size, establishing various forms of government, religion, today the global human population is estimated by the United Nations to be near 7.5 billion. In common usage, the word generally refers to the only extant species of the genus Homo—anatomically and behaviorally modern Homo sapiens. In scientific terms, the meanings of hominid and hominin have changed during the recent decades with advances in the discovery, there is also a distinction between anatomically modern humans and Archaic Homo sapiens, the earliest fossil members of the species. The English adjective human is a Middle English loanword from Old French humain, ultimately from Latin hūmānus, the words use as a noun dates to the 16th century. The native English term man can refer to the species generally, the species binomial Homo sapiens was coined by Carl Linnaeus in his 18th century work Systema Naturae. The generic name Homo is a learned 18th century derivation from Latin homō man, the species-name sapiens means wise or sapient. Note that the Latin word homo refers to humans of either gender, the genus Homo evolved and diverged from other hominins in Africa, after the human clade split from the chimpanzee lineage of the hominids branch of the primates. The closest living relatives of humans are chimpanzees and gorillas, with the sequencing of both the human and chimpanzee genome, current estimates of similarity between human and chimpanzee DNA sequences range between 95% and 99%. The gibbons and orangutans were the first groups to split from the leading to the humans. The splitting date between human and chimpanzee lineages is placed around 4–8 million years ago during the late Miocene epoch, during this split, chromosome 2 was formed from two other chromosomes, leaving humans with only 23 pairs of chromosomes, compared to 24 for the other apes. There is little evidence for the divergence of the gorilla, chimpanzee. Each of these species has been argued to be an ancestor of later hominins

30.
Car
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A car is a wheeled, self-powered motor vehicle used for transportation and a product of the automotive industry. The year 1886 is regarded as the year of the modern car. In that year, German inventor Karl Benz built the Benz Patent-Motorwagen, cars did not become widely available until the early 20th century. One of the first cars that was accessible to the masses was the 1908 Model T, an American car manufactured by the Ford Motor Company. Cars were rapidly adopted in the United States of America, where they replaced animal-drawn carriages and carts, cars are equipped with controls used for driving, parking, passenger comfort and safety, and controlling a variety of lights. Over the decades, additional features and controls have been added to vehicles, examples include rear reversing cameras, air conditioning, navigation systems, and in car entertainment. Most cars in use in the 2010s are propelled by a combustion engine. Both fuels cause air pollution and are blamed for contributing to climate change. Vehicles using alternative fuels such as ethanol flexible-fuel vehicles and natural gas vehicles are also gaining popularity in some countries, electric cars, which were invented early in the history of the car, began to become commercially available in 2008. There are costs and benefits to car use, the costs of car usage include the cost of, acquiring the vehicle, interest payments, repairs and auto maintenance, fuel, depreciation, driving time, parking fees, taxes, and insurance. The costs to society of car use include, maintaining roads, land use, road congestion, air pollution, public health, health care, road traffic accidents are the largest cause of injury-related deaths worldwide. The benefits may include transportation, mobility, independence. The ability for humans to move flexibly from place to place has far-reaching implications for the nature of societies and it was estimated in 2010 that the number of cars had risen to over 1 billion vehicles, up from the 500 million of 1986. The numbers are increasing rapidly, especially in China, India, the word car is believed to originate from the Latin word carrus or carrum, or the Middle English word carre. In turn, these originated from the Gaulish word karros, the Gaulish language was a branch of the Brythoic language which also used the word Karr, the Brythonig language evolved into Welsh where Car llusg and car rhyfel still survive. It originally referred to any wheeled vehicle, such as a cart, carriage. Motor car is attested from 1895, and is the formal name for cars in British English. Autocar is a variant that is attested from 1895

31.
Sperm whale
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The sperm whale, or cachalot, is the largest of the toothed whales and the largest toothed predator. It is the only living member of genus Physeter, and one of three extant species in the whale family, along with the pygmy sperm whale and dwarf sperm whale of the genus Kogia. Mature males average 16 metres in length but some may reach 20.5 metres, plunging to 2,250 metres, it is the second deepest diving mammal, following only the Cuviers beaked whale. The sperm whales clicking vocalization, a form of echolocation and communication and it has the largest brain of any animal on Earth, more than five times heavier than a humans. Sperm whales can live for more than 60 years, the sperm whale can be found anywhere in the open ocean. Females and young males live together in groups while males live solitary lives outside of the mating season. The females cooperate to protect and nurse their young, females give birth every four to twenty years, and care for the calves for more than a decade. A mature sperm whale has few predators, although calves. From the early eighteenth century through the late 20th, the species was a target of whalers. The head of the whale contains a liquid wax called spermaceti, spermaceti was used in lubricants, oil lamps, and candles. Ambergris, a product from its digestive system, is still used as a fixative in perfumes. Occasionally the sperm whales great size allowed it to defend effectively against whalers. The species is now protected by a moratorium, and is currently listed as vulnerable by the International Union for the Conservation of Nature. The name sperm whale is a clip of spermaceti whale, spermaceti, originally mistakenly identified as the whales semen, is the semi-liquid, waxy substance found within the whales head. The sperm whale is known as the cachalot, which is thought to derive from the archaic French for tooth or big teeth. The etymological dictionary of Corominas says the origin is uncertain, but it suggests that it comes from the Vulgar Latin cappula, plural of cappulum, the word cachalot came to English via French from Spanish or Portuguese cachalote, perhaps from Galician/Portuguese cachola, big head. The term is retained in the Russian word for the animal, кашалот, the scientific genus name Physeter comes from Greek physētēr, meaning blowpipe, blowhole, or – as a pars pro toto – whale. The specific name macrocephalus is Latinized from the Greek makrokephalos, from makros + kefalos and its synonymous specific name catodon means down-tooth, from the Greek elements cat- and odṓn, so named because it has visible teeth only in its lower jaw

32.
Association football
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Association football, more commonly known as football or soccer, is a team sport played between two teams of eleven players with a spherical ball. It is played by 250 million players in over 200 countries and dependencies making it the worlds most popular sport, the game is played on a rectangular field with a goal at each end. The object of the game is to score by getting the ball into the opposing goal, players are not allowed to touch the ball with their hands or arms while it is in play, unless they are goalkeepers. Other players mainly use their feet to strike or pass the ball, the team that scores the most goals by the end of the match wins. If the score is level at the end of the game, the Laws of the Game were originally codified in England by The Football Association in 1863. Association football is governed internationally by the International Federation of Association Football, the first written reference to the inflated ball used in the game was in the mid-14th century, Þe heued fro þe body went, Als it were a foteballe. The Online Etymology Dictionary states that the word soccer was split off in 1863, according to Partha Mazumdar, the term soccer originated in England, first appearing in the 1880s as an Oxford -er abbreviation of the word association. Within the English-speaking world, association football is now usually called football in the United Kingdom and mainly soccer in Canada and the United States. People in Australia, Ireland, South Africa and New Zealand use either or both terms, although national associations in Australia and New Zealand now primarily use football for the formal name. According to FIFA, the Chinese competitive game cuju is the earliest form of football for which there is scientific evidence, cuju players could use any part of the body apart from hands and the intent was kicking a ball through an opening into a net. It was remarkably similar to football, though similarities to rugby occurred. During the Han Dynasty, cuju games were standardised and rules were established, phaininda and episkyros were Greek ball games. An image of an episkyros player depicted in low relief on a vase at the National Archaeological Museum of Athens appears on the UEFA European Championship Cup, athenaeus, writing in 228 AD, referenced the Roman ball game harpastum. Phaininda, episkyros and harpastum were played involving hands and violence and they all appear to have resembled rugby football, wrestling and volleyball more than what is recognizable as modern football. As with pre-codified mob football, the antecedent of all football codes. Non-competitive games included kemari in Japan, chuk-guk in Korea and woggabaliri in Australia, Association football in itself does not have a classical history. Notwithstanding any similarities to other games played around the world FIFA have recognised that no historical connection exists with any game played in antiquity outside Europe. The modern rules of football are based on the mid-19th century efforts to standardise the widely varying forms of football played in the public schools of England

33.
Eiffel Tower
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The Eiffel Tower is a wrought iron lattice tower on the Champ de Mars in Paris, France. It is named after the engineer Gustave Eiffel, whose company designed, the Eiffel Tower is the most-visited paid monument in the world,6.91 million people ascended it in 2015. The tower is 324 metres tall, about the height as an 81-storey building. Its base is square, measuring 125 metres on each side, due to the addition of a broadcasting aerial at the top of the tower in 1957, it is now taller than the Chrysler Building by 5.2 metres. Excluding transmitters, the Eiffel Tower is the second-tallest structure in France after the Millau Viaduct, the tower has three levels for visitors, with restaurants on the first and second levels. The top levels upper platform is 276 m above the ground – the highest observation deck accessible to the public in the European Union, tickets can be purchased to ascend by stairs or lift to the first and second levels. The climb from ground level to the first level is over 300 steps, although there is a staircase to the top level, it is usually only accessible by lift. Eiffel openly acknowledged that inspiration for a tower came from the Latting Observatory built in New York City in 1853, sauvestre added decorative arches to the base of the tower, a glass pavilion to the first level, and other embellishments. Little progress was made until 1886, when Jules Grévy was re-elected as president of France and Édouard Lockroy was appointed as minister for trade. On 12 May, a commission was set up to examine Eiffels scheme and its rivals, which, after some debate about the exact location of the tower, a contract was signed on 8 January 1887. Eiffel was to all income from the commercial exploitation of the tower during the exhibition. He later established a company to manage the tower, putting up half the necessary capital himself. The proposed tower had been a subject of controversy, drawing criticism from those who did not believe it was feasible and these objections were an expression of a long-standing debate in France about the relationship between architecture and engineering. And for twenty years … we shall see stretching like a blot of ink the hateful shadow of the column of bolted sheet metal. Gustave Eiffel responded to criticisms by comparing his tower to the Egyptian pyramids. Will it not also be grandiose in its way, and why would something admirable in Egypt become hideous and ridiculous in Paris. Indeed, Garnier was a member of the Tower Commission that had examined the various proposals, some of the protesters changed their minds when the tower was built, others remained unconvinced. Guy de Maupassant supposedly ate lunch in the restaurant every day because it was the one place in Paris where the tower was not visible

34.
Kilometre
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The kilometre or kilometer is a unit of length in the metric system, equal to one thousand metres. K is occasionally used in some English-speaking countries as an alternative for the kilometre in colloquial writing. A slang term for the kilometre in the US military is klick, there are two common pronunciations for the word. It is generally preferred by the British Broadcasting Corporation and the Australian Broadcasting Corporation, many scientists and other users, particularly in countries where the metric system is not widely used, use the pronunciation with stress on the second syllable. The latter pronunciation follows the pattern used for the names of measuring instruments. The problem with this reasoning, however, is that the meter in those usages refers to a measuring device. The contrast is more obvious in countries using the British rather than American spelling of the word metre. When Australia introduced the system in 1975, the first pronunciation was declared official by the governments Metric Conversion Board. However, the Australian prime minister at the time, Gough Whitlam, by the 8 May 1790 decree, the Constituent assembly ordered the French Academy of Sciences to develop a new measurement system. In August 1793, the French National Convention decreed the metre as the length measurement system in the French Republic. The first name of the kilometre was Millaire, although the metre was formally defined in 1799, the myriametre was preferred to the kilometre for everyday use. The term myriamètre appeared a number of times in the text of Develeys book Physique dEmile, ou, Principes de la de la nature. French maps published in 1835 had scales showing myriametres and lieues de Poste, the Dutch, on the other hand, adopted the kilometre in 1817 but gave it the local name of the mijl. It was only in 1867 that the term became the only official unit of measure in the Netherlands to represent 1000 metres. In the US, the National Highway System Designation Act of 1995 prohibits the use of highway funds to convert existing signs or purchase new signs with metric units. Although the State DOTs had the option of using metric measurements or dual units, all of them abandoned metric measurements, the Manual on Uniform Traffic Control Devices since 2000 is published in both metric and American Customary Units. Some sporting disciplines feature 1000 m races in major events, but in other disciplines, even though records are catalogued

35.
Mount Everest
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Mount Everest, also known in Nepal as Sagarmāthā and in China as Chomolungma/珠穆朗玛峰, is Earths highest mountain. Its peak is 8,848 metres above sea level, Mount Everest is in the Mahalangur Range. The international border between China and Nepal runs across Everests summit point and its massif includes neighbouring peaks Lhotse,8,516 m, Nuptse,7,855 m, and Changtse,7,580 m. In 1856, the Great Trigonometrical Survey of India established the first published height of Everest, then known as Peak XV, at 8,840 m. The current official height of 8,848 m as recognised by China and Nepal was established by a 1955 Indian survey, in 2005, China remeasured the height of the mountain and got a result of 8844.43 m. An argument regarding the height between China and Nepal lasted five years from 2005 to 2010, China argued it should be measured by its rock height which is 8,844 m but Nepal said it should be measured by its snow height 8,848 m. In 2010, an agreement was reached by both sides that the height of Everest is 8,848 m and Nepal recognises Chinas claim that the rock height of Everest is 8,844 m. In 1865, Everest was given its official English name by the Royal Geographical Society upon a recommendation by Andrew Waugh, the British Surveyor General of India. As there appeared to be several different local names, Waugh chose to name the mountain after his predecessor in the post, Sir George Everest, Mount Everest attracts many climbers, some of them highly experienced mountaineers. There are two main climbing routes, one approaching the summit from the southeast in Nepal and the other from the north in Tibet, as of 2016 there are well over 200 corpses on the mountain, with some of them even serving as landmarks. The first recorded efforts to reach Everests summit were made by British mountaineers, with Nepal not allowing foreigners into the country at the time, the British made several attempts on the north ridge route from the Tibetan side. Tragedy struck on the descent from the North Col when seven porters were killed in an avalanche. They had been spotted high on the mountain that day but disappeared in the clouds, never to be seen again, Tenzing Norgay and Edmund Hillary made the first official ascent of Everest in 1953 using the southeast ridge route. Tenzing had reached 8,595 m the previous year as a member of the 1952 Swiss expedition, the Chinese mountaineering team of Wang Fuzhou, Gonpo, and Qu Yinhua made the first reported ascent of the peak from the north ridge on 25 May 1960. In 1802, the British began the Great Trigonometric Survey of India to fix the locations, heights, starting in southern India, the survey teams moved northward using giant theodolites, each weighing 500 kg and requiring 12 men to carry, to measure heights as accurately as possible. They reached the Himalayan foothills by the 1830s, but Nepal was unwilling to allow the British to enter the country due to suspicions of political aggression, several requests by the surveyors to enter Nepal were turned down. The British were forced to continue their observations from Terai, a region south of Nepal which is parallel to the Himalayas, conditions in Terai were difficult because of torrential rains and malaria. Three survey officers died from malaria while two others had to retire because of failing health, nonetheless, in 1847, the British continued the survey and began detailed observations of the Himalayan peaks from observation stations up to 240 km distant

36.
Panama Canal
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The Panama Canal is an artificial 48-mile waterway in Panama that connects the Atlantic Ocean with the Pacific Ocean. The canal cuts across the Isthmus of Panama and is a key conduit for maritime trade. The original locks are 33.5 metres wide, a third, wider lane of locks was constructed between September 2007 and May 2016. The expanded canal began operation on June 26,2016. The new locks allow transit of larger, Post-Panamax ships, capable of handling more cargo, France began work on the canal in 1881 but stopped due to engineering problems and a high worker mortality rate. The United States took over the project in 1904 and opened the canal on August 15,1914, Colombia, France, and later the United States controlled the territory surrounding the canal during construction. The U. S. continued to control the canal and surrounding Panama Canal Zone until the 1977 Torrijos–Carter Treaties provided for handover to Panama. After a period of joint American–Panamanian control, in 1999 the canal was taken over by the Panamanian government and is now managed and operated by the government-owned Panama Canal Authority. Annual traffic has risen from about 1,000 ships in 1914, by 2012, more than 815,000 vessels had passed through the canal. It takes six to eight hours to pass through the Panama Canal, the American Society of Civil Engineers has called the Panama Canal one of the seven wonders of the modern world. Such a route would have given the Spanish a military advantage over the Portuguese, during an expedition from 1788 to 1793, Alessandro Malaspina outlined plans for its construction. Given the strategic location of Panama and the potential offered by its narrow isthmus separating two great oceans, other links in the area were attempted over the years. The ill-fated Darien scheme was launched by the Kingdom of Scotland in 1698 to set up a trade route. Generally inhospitable conditions thwarted the effort, and it was abandoned in April 1700, another effort was made in 1843. They referred to it as the Atlantic and Pacific Canal and it was a wholly British endeavor and it was expected to be completed in five years, but the plan was never carried out. At nearly the same time, other ideas were floated, including a canal across Mexicos Isthmus of Tehuantepec. Nothing came of that plan either. )In 1846 the Mallarino–Bidlack Treaty, negotiated between the U. S. and New Granada, granted the United States transit rights and the right to intervene militarily in the isthmus. In 1849, the discovery of gold in California created great interest in a crossing between the Atlantic and Pacific Oceans, the Panama Railway was built by the United States to cross the isthmus and opened in 1855

37.
Trans-Siberian Railway
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The Trans-Siberian Railway is a network of railways connecting Moscow with the Russian Far East. With a length of 9,289 kilometres, it is the longest railway line in the world, there are connecting branch lines into Mongolia, China and North Korea. It has connected Moscow with Vladivostok since 1916, and is still being expanded and it was built between 1891 and 1916 under the supervision of Russian government ministers personally appointed by Tsar Alexander III and his son, the Tsarevich Nicholas. Even before it had completed, it attracted travellers who wrote of their adventures. Russia has expressed its desire for Pakistan to participate in the China–Pakistan Economic Corridor, the railway is often associated with the main transcontinental Russian line that connects hundreds of large and small cities of the European and Asian parts of Russia. At a Moscow-Vladivostok track length of 9,289 kilometres, it spans a record eight time zones, a second primary route is the Trans-Manchurian, which coincides with the Trans-Siberian east of Chita as far as Tarskaya, about 1,000 km east of Lake Baikal. From Tarskaya the Trans-Manchurian heads southeast, via Harbin and Mudanjiang in Chinas Northeastern Provinces and this is the shortest and the oldest railway route to Vladivostok. While there are currently no passenger services on this branch. The third primary route is the Trans-Mongolian Railway, which coincides with the Trans-Siberian as far as Ulan-Ude on Lake Baikals eastern shore, from Ulan-Ude the Trans-Mongolian heads south to Ulaan-Baatar before making its way southeast to Beijing. In 1991, a route running further to the north was finally completed. Known as the Baikal Amur Mainline, this recent extension departs from the Trans-Siberian line at Taishet several hundred miles west of Lake Baikal and it crosses the Amur River at Komsomolsk-na-Amure, and reaches the Tatar Strait at Sovetskaya Gavan. On 13 October 2011, a train from Khasan made its run to Rajin. In the late 19th century, the development of Siberia was hampered by poor transport links within the region, aside from the Great Siberian Route, good roads suitable for wheeled transport were rare. For about five months of the year, rivers were the means of transport. During the cold half of the year, cargo and passengers travelled by horse-drawn sledges over the roads, many of which were the same rivers. The first steamboat on the River Ob, Nikita Myasnikovs Osnova, was launched in 1844, but early beginnings were difficult, and it was not until 1857 that steamboat shipping started developing on the Ob system in a serious way. Steamboats started operating on the Yenisei in 1863, and on the Lena, an attempt to partially remedy the situation by building the Ob-Yenisei Canal was not particularly successful. Only a railway could be a solution to the regions transport problems

38.
Asteroid
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Asteroids are minor planets, especially those of the inner Solar System. The larger ones have also been called planetoids and these terms have historically been applied to any astronomical object orbiting the Sun that did not show the disc of a planet and was not observed to have the characteristics of an active comet. As minor planets in the outer Solar System were discovered and found to have volatile-based surfaces that resemble those of comets, in this article, the term asteroid refers to the minor planets of the inner Solar System including those co-orbital with Jupiter. There are millions of asteroids, many thought to be the remnants of planetesimals. The large majority of known asteroids orbit in the belt between the orbits of Mars and Jupiter, or are co-orbital with Jupiter. However, other orbital families exist with significant populations, including the near-Earth objects, individual asteroids are classified by their characteristic spectra, with the majority falling into three main groups, C-type, M-type, and S-type. These were named after and are identified with carbon-rich, metallic. The size of asteroids varies greatly, some reaching as much as 1000 km across, asteroids are differentiated from comets and meteoroids. In the case of comets, the difference is one of composition, while asteroids are composed of mineral and rock, comets are composed of dust. In addition, asteroids formed closer to the sun, preventing the development of the aforementioned cometary ice, the difference between asteroids and meteoroids is mainly one of size, meteoroids have a diameter of less than one meter, whereas asteroids have a diameter of greater than one meter. Finally, meteoroids can be composed of either cometary or asteroidal materials, only one asteroid,4 Vesta, which has a relatively reflective surface, is normally visible to the naked eye, and this only in very dark skies when it is favorably positioned. Rarely, small asteroids passing close to Earth may be visible to the eye for a short time. As of March 2016, the Minor Planet Center had data on more than 1.3 million objects in the inner and outer Solar System, the United Nations declared June 30 as International Asteroid Day to educate the public about asteroids. The date of International Asteroid Day commemorates the anniversary of the Tunguska asteroid impact over Siberia, the first asteroid to be discovered, Ceres, was found in 1801 by Giuseppe Piazzi, and was originally considered to be a new planet. In the early half of the nineteenth century, the terms asteroid. Asteroid discovery methods have improved over the past two centuries. This task required that hand-drawn sky charts be prepared for all stars in the band down to an agreed-upon limit of faintness. On subsequent nights, the sky would be charted again and any moving object would, hopefully, the expected motion of the missing planet was about 30 seconds of arc per hour, readily discernible by observers

39.
Moon
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The Moon is an astronomical body that orbits planet Earth, being Earths only permanent natural satellite. It is the fifth-largest natural satellite in the Solar System, following Jupiters satellite Io, the Moon is second-densest satellite among those whose densities are known. The average distance of the Moon from the Earth is 384,400 km, the Moon is thought to have formed about 4.51 billion years ago, not long after Earth. It is the second-brightest regularly visible celestial object in Earths sky, after the Sun and its surface is actually dark, although compared to the night sky it appears very bright, with a reflectance just slightly higher than that of worn asphalt. Its prominence in the sky and its cycle of phases have made the Moon an important cultural influence since ancient times on language, calendars, art. The Moons gravitational influence produces the ocean tides, body tides, and this matching of apparent visual size will not continue in the far future. The Moons linear distance from Earth is currently increasing at a rate of 3.82 ±0.07 centimetres per year, since the Apollo 17 mission in 1972, the Moon has been visited only by uncrewed spacecraft. The usual English proper name for Earths natural satellite is the Moon, the noun moon is derived from moone, which developed from mone, which is derived from Old English mōna, which ultimately stems from Proto-Germanic *mǣnōn, like all Germanic language cognates. Occasionally, the name Luna is used, in literature, especially science fiction, Luna is used to distinguish it from other moons, while in poetry, the name has been used to denote personification of our moon. The principal modern English adjective pertaining to the Moon is lunar, a less common adjective is selenic, derived from the Ancient Greek Selene, from which is derived the prefix seleno-. Both the Greek Selene and the Roman goddess Diana were alternatively called Cynthia, the names Luna, Cynthia, and Selene are reflected in terminology for lunar orbits in words such as apolune, pericynthion, and selenocentric. The name Diana is connected to dies meaning day, several mechanisms have been proposed for the Moons formation 4.51 billion years ago, and some 60 million years after the origin of the Solar System. These hypotheses also cannot account for the angular momentum of the Earth–Moon system. This hypothesis, although not perfect, perhaps best explains the evidence, eighteen months prior to an October 1984 conference on lunar origins, Bill Hartmann, Roger Phillips, and Jeff Taylor challenged fellow lunar scientists, You have eighteen months. Go back to your Apollo data, go back to computer, do whatever you have to. Dont come to our conference unless you have something to say about the Moons birth, at the 1984 conference at Kona, Hawaii, the giant impact hypothesis emerged as the most popular. Afterward there were only two groups, the giant impact camp and the agnostics. Giant impacts are thought to have been common in the early Solar System, computer simulations of a giant impact have produced results that are consistent with the mass of the lunar core and the present angular momentum of the Earth–Moon system

40.
Light-second
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The light-second is a unit of length useful in astronomy, telecommunications and relativistic physics. It is defined as the distance light travels in free space in one second. One light-nanosecond is almost 300 millimetres, which limits the speed of transfer between different parts of a large computer. One light-microsecond is about 300 metres, the mean distance, over land, between opposite sides of the Earth is 66.8 light-milliseconds. Communications satellites are typically 1.337 light-milliseconds to 119.4 light-milliseconds from the surface of the Earth, the light-second is a convenient unit for measuring distances in the inner Solar System, because it corresponds very closely to the radiometric data used to determine them.004786385 s. The mean diameter of the Earth is about 0.0425 light-seconds, the average distance from the Earth to the Moon is about 1.282 light-seconds. The diameter of the Sun is about 4.643 light-seconds, the average distance from the Earth to the Sun is 499.0 light-seconds. Multiples of the light-second can be defined, although apart from the light-year they are used in popular science publications than in research works. For example, a light-minute is 60 light-seconds and the distance from the Earth to the Sun is 8.317 light-minutes. Light-year 100 megametres Geometrized unit system

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Sun
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The Sun is the star at the center of the Solar System. It is a perfect sphere of hot plasma, with internal convective motion that generates a magnetic field via a dynamo process. It is by far the most important source of energy for life on Earth. Its diameter is about 109 times that of Earth, and its mass is about 330,000 times that of Earth, accounting for about 99. 86% of the total mass of the Solar System. About three quarters of the Suns mass consists of hydrogen, the rest is mostly helium, with smaller quantities of heavier elements, including oxygen, carbon, neon. The Sun is a G-type main-sequence star based on its spectral class and it formed approximately 4.6 billion years ago from the gravitational collapse of matter within a region of a large molecular cloud. Most of this matter gathered in the center, whereas the rest flattened into a disk that became the Solar System. The central mass became so hot and dense that it eventually initiated nuclear fusion in its core and it is thought that almost all stars form by this process. The Sun is roughly middle-aged, it has not changed dramatically for more than four billion years and it is calculated that the Sun will become sufficiently large enough to engulf the current orbits of Mercury, Venus, and probably Earth. The enormous effect of the Sun on Earth has been recognized since prehistoric times, the synodic rotation of Earth and its orbit around the Sun are the basis of the solar calendar, which is the predominant calendar in use today. The English proper name Sun developed from Old English sunne and may be related to south, all Germanic terms for the Sun stem from Proto-Germanic *sunnōn. The English weekday name Sunday stems from Old English and is ultimately a result of a Germanic interpretation of Latin dies solis, the Latin name for the Sun, Sol, is not common in general English language use, the adjectival form is the related word solar. The term sol is used by planetary astronomers to refer to the duration of a solar day on another planet. A mean Earth solar day is approximately 24 hours, whereas a mean Martian sol is 24 hours,39 minutes, and 35.244 seconds. From at least the 4th Dynasty of Ancient Egypt, the Sun was worshipped as the god Ra, portrayed as a falcon-headed divinity surmounted by the solar disk, and surrounded by a serpent. In the New Empire period, the Sun became identified with the dung beetle, in the form of the Sun disc Aten, the Sun had a brief resurgence during the Amarna Period when it again became the preeminent, if not only, divinity for the Pharaoh Akhenaton. The Sun is viewed as a goddess in Germanic paganism, Sól/Sunna, in ancient Roman culture, Sunday was the day of the Sun god. It was adopted as the Sabbath day by Christians who did not have a Jewish background, the symbol of light was a pagan device adopted by Christians, and perhaps the most important one that did not come from Jewish traditions

Closeup of National Prototype Metre Bar No. 27, made in 1889 by the International Bureau of Weights and Measures (BIPM) and given to the United States, which served as the standard for defining all units of length in the US from 1893 to 1960

In physics, the wavelength of a sinusoidal wave is the spatial period of the wave—the distance over which the wave's …

Wavelength is decreased in a medium with slower propagation.

A wave on a line of atoms can be interpreted according to a variety of wavelengths.

Pattern of light intensity on a screen for light passing through two slits. The labels on the right refer to the difference of the path lengths from the two slits, which are idealized here as point sources.

A hypernova. Artist's illustration showing the life of a massive star as nuclear fusion converts lighter elements into heavier ones. When fusion no longer generates enough pressure to counteract gravity, the star rapidly collapses to form a black hole. Theoretically, energy may be released during the collapse along the axis of rotation to form a long duration gamma-ray burst.

Taking an X-ray image with early Crookes tube apparatus, late 1800s. The Crookes tube is visible in center. The standing man is viewing his hand with a fluoroscope screen. The seated man is taking a radiograph of his hand by placing it on a photographic plate. No precautions against radiation exposure are taken; its hazards were not known at the time.

1896 plaque published in "Nouvelle Iconographie de la Salpetrière", a medical journal. In the left a hand deformity, in the right same hand seen using radiography. The authors designated the technique as Röntgen photography.

The piano is an acoustic, stringed musical instrument invented in Italy by Bartolomeo Cristofori around the year 1700 …

Grand piano by Louis Bas of Villeneuve-lès-Avignon, France, 1781. Earliest French grand piano known to survive; includes an inverted wrestplank and action derived from the work of Bartolomeo Cristofori (ca. 1700) with ornately decorated soundboard.

The Sun is the star at the center of the Solar System. It is a nearly perfect sphere of hot plasma, with internal …

During a total solar eclipse, the solar corona can be seen with the naked eye, during the brief period of totality.

Taken by Hinode's Solar Optical Telescope on 12 January 2007, this image of the Sun reveals the filamentary nature of the plasma connecting regions of different magnetic polarity.

Visible light photograph of sunspot, 13 December 2006

In this false-color ultraviolet image, the Sun shows a C3-class solar flare (white area on upper left), a solar tsunami (wave-like structure, upper right) and multiple filaments of plasma following a magnetic field, rising from the stellar surface.

The ''Galileo'' Probe plunged deep into Jupiter in 1995. It was carried to the Jovian system by the ''Galileo'' spacecraft, where it was released and survived what was then the highest-velocity atmospheric entry yet attempted.

Real image of the northern hemisphere of Saturn, as taken by the Cassini–Huygens mission

The Milky Way arching at a high inclination across the night sky (fish-eye mosaic shot at Paranal, Chile). The bright object is Jupiter in the constellation Sagittarius, and the Magellanic Clouds can be seen on the left. Galactic north is downwards.

Spitzer reveals what cannot be seen in visible light: cooler stars (blue), heated dust (reddish hue), and Sgr A* as bright white spot in the middle.